Electrical apparatus



March 13, 1934. G. D. oNElLL ELECTRICAL APPARATUS Filed Nov. 1o.- 1951 Patented Mar. 13, 1934 OFFICE ELECTRICAL APPARATUS George Dean O'Neill, Beverly, Mass., assignor to Hygrade Sylvania Corporation, Salem, Mass., a

corporation of Massachusetts Application November 10, 1931, Serial No. 574,087 4 Claims. (Cl. Z50-27.5)

This invention relates to an improved radio tube, and more oi' the pentode type, having a suppressor grid between the screen grid and the plate.

Heretofore tubes of the pentode type have commonly been provided with 4iilament emitters, the suppressor grid return being connected to the mid-point of the iilament. The present invention provides an emitter of the indirectly-heated type, the filament, the cathode, the suppressor grid and connecting means therebetween being arranged so that high eiiiciency is obtained with simplicity of mechanical construction as well as an arrangement of connections which permits the employment of a conventional base, for example, of the live-prong type. To permit these desirable re-` sults the mid-point ofthe filament, which conveniently may be a U-shaped or non-inductively wound wire, is connected to the upper end oi a tubular cathode by a lead welded to the pinchedin end of the cathode, this lead being connected to the third or suppressor grid to provide a grid return. An arrangement of this character permits the third or suppressor grid to have a potential substantially the same as that of the emitter so that undesirable electrical characteristics are avoided, while secondary radiations from the plate are properly repelled by the third grid and prevented from aiecting the action of the screen grid. Furthermore, the advantages of an indirectly heated emitter or cathode are attained and the suppressor or third grid does not require the employment of an additional exterior connection to the tube so that a conventional tube socket may be employed.

In the accompanying drawing:

Figa 1 is a centralsectional view oi the electrodes and related connections of a tube constructed in accordance with this invention;

Fig. 2 is a top plan view of the assembly shown in Fig. l;

Fig. 3 is an elevational detail of the filament and the lead connected to the mid point thereof before the same are assembled with the cathode;

Fig. 4 is a vertical section through the cathode showing the assembly of the filament and grid return connection therewith;

Fig. 5 is a schematic view of the tube and its connections; and

Fig. 6 is an enlarged section on line 6-6 of Fig. 4.

In the accompanying drawing, the numeral 1 designates the conventional non-conductive or glass base upon which the various electrodes of my improved tube are mounted. As shown more particularly to an improved tube formed in the conventional manner of substantially semi-circular the plate 3 and be particularly in Figs. 1 and 2. the'plateA 3 may be metal sheet or meshe'd screen elements 3a and 3b with outstandingiianges 4 connected to vertical supporting wires 5, one oi these wires being extended to provide an exterior connection 5a (Fig. 5). Extending between the Wires 5 are horizontal grid-supporting strips 9 o1 insulating material, such as mica. A cylindrical grid 10 may conveniently be disposed within provided with an upwardly extending return element 14 as well as with projecting elements 16 extending through openings in the strips 9. The screen grid 17 may similarly be arranged within the suppressive grid 10, being provided with a depending lead or return connection 18. Within the screen grid 1'? is the control grid 19 which may also be of similar form and is provided with a depending connection 21.

Centrally disposed within the concentrically arranged plate 3, the grids 10, 17 and 19, is the emitter assembly 25. The latter includes a nlament 26 which may be conveniently formed by folding a line wire to provide parallel elements 26 which may be coated with suitable insulating material 27, such as aluminum oxide. At the i'old point a lead 29 is secured. Thus, in eiect, the niament proper is substantially U-shaped with the lead 29 secured to its mid-point. The iilament thus provided is disposed within a suitably coated metallic cathode tube 31. The upper end of this metal tube is pinched upon the lead 29, as designated by the numeral 32, and is welded thereto, The lead 29 may have its upper end bent at right angles to the vertical extent of the tube and be welded to the lead 14 projecting upwardly from the third grid 10. Thus the leads 14 and 29 cooperate in providing a grid return so that the suppressor grid 10 possesses substantially the same potential as the cathode 31 and so that a grid return is provided through the connections for the lainent 27, which are designated by numeral 35.

Fig. 5 diagrammatically illustrates the arrangement of the tube elements and connections, the iilament leads 35 being connected in the conventional manner to the two legs 26a of the filament, the mid-portion of the latter being connected to the upper end of the cathode 31 and by the leads 29 and 14 to the third grid 10. It is thus evident that a pentode tube of this character requires but ve exterior connections, namely, the connection 5a for the plate 3, the connection 18 for the screen grid 17, the connection 21 for the control grid 19, and the 'iilament connections 35 which also serve to aiord a grid return. Thus a conventional five-pronged base to engage a standard five-prong socket may be employed with a tube of this type.

It accordingly is evident that I have provided a tube having the advantages of a pentode or suppressor grid arrangement together with the advantages of an indirectly heated cathode, while avoiding the necessity of added connections to the electrodes within the tube so that a tube of this character may be used with standard socket equipment. y

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

' I claim:

1. A vacuum tube comprising a grid, a tubular electron emitter, a folded heating filament inside the tubular emitter, and a lead extending directly from the fold of the filament through one end of the tubular electrode to said grid, characterized in that said end of the emitter is pinched and welded to said lead, whereby both the grid and the emitter are connected to the external circuit through the filament connections thereby avoiding adverse operating characteristics caused by separate connector.

2. A tube of the pentode type comprising a suppressor grid, a tubular electron emitter, a folded heating filament inside the tubular emitter, and a lead directly interconnecting the grid and emitter with the mid-point of the filament, the lead extending through one end of the tubular emitter and said end being pinched and welded to said lead.

3. A tube of the pentode type comprising a control grid, a shield grid, a suppressor grid, an anode, a hollow electron emitter, an interior filament for heating the emitter, and a single lead directly interconnecting the suppressor grid and emitter with the mid-point of the lament through an opening in the hollow emitter. 4. In combination, a uni-potential cathode including a metallic sleeve and a lamentary heater within said sleeve, a control grid surrounding said cathode, a shield grid shielding said control grid, a suppressor grid surrounding said shield grid, an anode surrounding said suppressor grid, and a Wire connected at one end to the midpoint of said filament, and said shield, and at the other end to said suppressor grid, whereby said suppressor grid is at substantially the same average potential as said cathode.

GEORGE DEAN ONEILL. 

